endo-exo convention 1) the position of double bonds relative to rings in carbocyclic systems; 2) the...
TRANSCRIPT
Endo-Exo Convention1) the position of double bonds relative to rings in carbocyclic systems; 2) the relative orientation of substituents ofbridged carbocycles; 3) opposing pathways for certain intramolecularcyclization and cleavage reactions; 4) opposing pathways for Diels-Alder type cycloaddition reactions based on theorientation of dienes to dieneophiles.
endocyclic exocyclic
Alkene Orientations
Ring Bridging1) a bridge containing a heteroatom or atoms2) a shorter bridge3) a saturated bridge4) a less substituted bridge5) a bridge with the lowest CIP priority substituents
O
W W
O
W W
CH3
CH3
W W
O
W W
HO CH3
endo endo exo
exoexo exoendo
endo
INTRAMOLECULAR CYCLIZATIONS
endocyclic addition
exocyclic addition
Example 1. Endocyclic and exocyclic double bonds: In the compound chamigrene, which was stereoselectively synthesized by transannular cyclopropanation followed by ring fragmentation, there is both an endocyclic double bond and an exocyclic double bond
Example 2. 2,6-Dimethylbicyclo[3.3.1]nona-3,7-diene-endo-2,endo-6-diol. The short bridge takes precedence over the unsaturated bridges
H3C
HO
CH3
OH
For each bridged compound below, identify thereference bridge and specify the endo/exo orientationof "W" substituent
NH
W
NH2O
W
O WOEt
Br
OHH3CO
W
H3CCH3
W
WH3C
CH3
W
H3CCH3
HO
W COOH O
W
(a) (b)
(d)
(h)
(f)
(c)
(e)
(g) (i)